The number of electrically operated vehicles will increase in the future. In this context, a stepwise transition from fossil fuels to electrical vehicle drives is to be observed. The application of the invention is, for example, expedient in hybrid electrical vehicles (HEVs), battery-electrical vehicles (BEVs) as well as in fuel-cell vehicles (FCVs).
Since in the next years and decades the number of electrically operated vehicles, particularly with electrical primary drives, will increase, the demands on the vehicle electrical systems are changing significantly. Crucial for the acceptance of electrical drives are in this case reliability as well as safety of the high-voltage vehicle electrical system.
Depending on the degree of electrification, i.e. what proportion of the drive power is electrical, the electrical power lies in the range of between 10 and 120 kW. Compared with conventional 12 V vehicle electrical systems, the operating voltage in the vehicle electrical systems of electrically operated vehicles is much higher. This is made possible by the integration of high-voltage batteries as chargeable energy storage units. Because of the much higher operating voltages, the complexity of the vehicle electrical system increases, and therefore so do the demands on the vehicle electrical components such as relays, lines and fuses.
Particularly at safety-critical times, reliable disconnection of the high-voltage vehicle electrical system from the high-voltage battery is a very essential point. For voltages of up to 1000 V DC and short-circuit currents in the kiloampere range, the demands on switching relays and fuses are considerable. Reliable switching behaviour of the relays as well as of the fuses must be ensured both in the normal situation and in the event of an accident. In the operating situation, switching is required at much lower currents than in the event of an accident or a fault. In the operating situation, i.e. for example during servicing and maintenance, although DC isolation must take place, the currents to be switched are however relatively low. Disconnection may be made possible by means of switching relays in the operating situation, or event in other special situations in which no short-circuit current flows, by means of switching relays.
In the event of a short circuit, however, much higher currents flow, and reliable disconnection must be possible even then. Conventionally, to this end a combination of fuses and relays is used both on the high side and on the low side. The fuses are used for disconnection in the event of a short circuit, whereas the relays are generally used for disconnection in the operating situation.
According to the subject matter, it has been found that the conventional combination of a fuse and a relay entails considerable outlay. The configuration of the respective combination of a fuse and relay must be mutually matched in order to ensure reliable tripping of the fuse even in the event of a short circuit. This leads to great demands on the tripping characteristics of relays and fuses, which leads to a considerable cost disadvantage.
It was therefore the object of the subject matter to provide a fuse for a high-voltage vehicle electrical system, which allows reliable short-circuit disconnection with low component costs.